Add tab navigation for building and recruitment UI

- Add selection indices and option lists to SkirmishState.
- Implement `cycle_popup_option` and expose Left/Right actions in
  keybindings.
- Introduce `cancel_focused_tasks` in BoardState for Delete handling.
- CellWidget now displays recruitment progress on Base structures.
- Update README and documentation to describe new tabs and arrow
  navigation.
- Adjust test counts and add extensive task‑cancellation tests.

src/app/widgets/board.rs

@@ -1,10 +1,11 @@
-use crate::app::states::skirmish_states::BoardState;
+use crate::app::states::skirmish_states::{BoardState, Players, tasks::Task, units::Unit};
+use crate::app::widgets::CellWidget;
 use ratatui::{
     buffer::Buffer,
     layout::{Constraint, Layout, Rect},
     widgets::Widget,
 };
-use std::rc::Rc;
+use std::{collections::HashSet, rc::Rc};
 
 pub struct BoardWidget<'a> {
     state: &'a BoardState,
@@ -18,6 +19,18 @@ impl<'a> BoardWidget<'a> {
 
 impl Widget for BoardWidget<'_> {
     fn render(self, area: Rect, buf: &mut Buffer) {
+        let mut queued_path: HashSet<(usize, usize)> = HashSet::new();
+        for row in &self.state.cells {
+            for cell in row {
+                if let Some(unit) = cell.get_ref_option_unit()
+                    && unit.get_owner() == Players::Player
+                {
+                    for task in unit.get_ref_tasks() {
+                        queued_path.extend(task.get_path().iter().copied());
+                    }
+                }
+            }
+        }
         let horizontal: Rc<[Rect]> =
             Layout::horizontal(vec![
                 Constraint::Length(self.state.cell_width as u16);
@@ -38,7 +51,17 @@ impl Widget for BoardWidget<'_> {
                     .cells
                     .get(row_idx + self.state.vertical_offset.get_value())
                     .and_then(|rows| rows.get(col_idx + self.state.horizontal_offset.get_value()))
-                    .map(|cell| cell.clone().render(*cell_area, buf));
+                    .map(|cell: &CellWidget| -> () {
+                        let mut cell: CellWidget = cell.clone();
+                        let coords: (usize, usize) = (
+                            row_idx + self.state.vertical_offset.get_value(),
+                            col_idx + self.state.horizontal_offset.get_value(),
+                        );
+                        if queued_path.contains(&coords) {
+                            cell.set_marked(true);
+                        }
+                        cell.render(*cell_area, buf);
+                    });
             }
         }
     }